Trans-Siberian Orchestra, 1996+
Not to be confused with that other instrumental group associated with the holidays, Trans-Siberian Orchestra was conceived by Paul O’Neill. In his own words: “The whole idea was to create a progressive rock band that would push the boundaries (of the genre) further than any group before… Way, way further.”
For comparison’s sake, here is the “Carol of the Bells” inspired Christmas Eve/Sarajevo. I posted Mannheim Steamroller’s version on Day 13.